Northern Exposure

Scientists are still shedding light on the many ways birds make use of habitat on Alaska's Arctic coastal plain

08-01-2003
//
Lisa W. Drew

AFTER STUDYING golden eagles in Alaska’s Denali National Park for a decade, Carol McIntyre still had three questions about her younger study subjects: Where do they go when they migrate south for their first winter? How many survive? And where do they go when they return north for the summer?

To find out, the National Park Service biologist outfitted 45 of Denali’s young golden eagles with tiny satellite transmitters and tracked their movements from 1997 to 2000. She discovered that in winter the birds dispersed all over the place, from California to Colorado and even Mexico. Many died from starvation (possibly related to habitat loss) and from electrocution on utility poles. In summer, surviving eagles returned to Alaska. And that’s when they truly surprised McIntyre. As she watched the blips of the 12 birds move north on her computer screen, five flew right past their original home in Interior Alaska and kept on going—beyond the Arctic Circle, over the Brooks Range and onto the state’s Arctic coastal plain. "We know now," says McIntyre, "that birds from the central region of the state will wander a lot farther than we thought they would and will summer on the coastal plain."

The eagles have plenty of company. About 100 avian species migrate to this region every summer to breed, taking advantage of its constant light, unique landforms, insect explosions, meltwater ponds, coastal lagoons and a host of other seasonal attractions. (They share this Arctic splendor, of course, with caribou, muskoxen, bears, wolves, lemmings and lots of other wildlife.) Although the rest of the state also draws plenty of migrating birds, this is the only place some species breed, molt or fatten up before flying south for the winter—and sometimes only in particular areas.

On the coastal plain of the Arctic National Wildlife Refuge, for example, as many as 300,000 snow geese congregate every September to feast on cottongrass and other plants. The geese stop here after nesting in Canada, often quadrupling their fat reserves before flying to California and other points south for the winter. To the west, high cliffs overlooking the coastal plain’s largest river, the Colville, host one of the world’s densest concentrations of nesting raptors, including peregrine falcons, rough-legged hawks and gyrfalcons.

ARCTIC BREEDER: Easy to miss in the tundra, a semipalmated plover (left) nests among flowers of bog laurel and mountain aven.

It’s only natural that bird researchers also flock to the Arctic coastal plain, whether they, like McIntyre, are figuratively present as they use computers to track transmitter-bearing birds or are on the ground coping with hordes of mosquitoes as they count birds in intensive surveys. Much of this research is aimed at "just trying to figure out what’s there and how many," says ornithologist Philip Martin with the U.S. Fish and Wildlife Service in Fairbanks. In part that’s because this region is rich with deposits of oil and natural gas, and knowledge of birds’ whereabouts and numbers could help influence critical decisions about the habitat’s future.

Arguably the most contentious of those decisions will concern what’s known as the 1002 Area, a piece of the Arctic National Wildlife Refuge that Congress could approve for oil development, and portions of the National Petroleum Reserve–Alaska (NPR–A) that are particularly rich in wildlife. The reserve is one of four U.S. regions, set aside in 1923, thought to contain significant amounts of oil. So far only exploratory wells have been drilled in the 37,000-square-mile reserve, but no oil has been extracted. As of April, the federal government was considering relaxing drilling restrictions around the NPR–A’s Teshekpuk Lake, an important site for tens of thousands of molting geese, including up to 20 percent of all Pacific black brants.

Although the Arctic Circle is the official line that separates the Arctic from the rest of the world, the practical dividing line for birds that summer on Alaska’s Arctic coastal plain is the Brooks Range. This 700-mile-wide, treeless strip of mountains reaches across the entire state just north of the Arctic Circle. On the north side of the Brooks Range, the coastal plain—often called the North Slope—can still be frozen in winter when the south side is already experiencing spring. Says waterfowl biologist Tom Rothe of the Alaska Department of Fish and Game, "I’ve been on the Colville Delta waiting for ducks and geese to arrive, and I’ve seen them come out of warm, sheltered mountain valleys during the day, check out the conditions and then go back at night."

CAMOUFLAGED: Western sandpiper eggs sit among early blooms of Lapland rose-bay.

Once summer arrives, near-constant sunlight defrosts a delicate skin of land and water that sits on top of permanently frozen soil and ice. This skin, which freezes solid for most of the year, is shaped by cycles of freezing and thawing. Over time, water and ice carve and build troughs and ridges that can form polygons some 30 to 60 feet across. "The difference between the center of a polygon and the trough between two polygons is terrific," says ecologist Dave Norton of the University of Alaska–Fairbanks. "There are huge gradients of moisture. From one side of a polygon to another, you can go from rain forest to desert." For birds, that means an abundance of closely spaced habitat options that draw diverse species that live practically side by side.

When the skin defrosts, it also opens up a refrigerator. "Part of the reason the habitat is so rich is that it’s an enormous icebox for keeping fast food on tap for the birds," says Norton. Different species can live in close proximity by eating different foods. Shorebirds, for example, specialize in different kinds of larval underground insects. "The ones with longer bills are generally going to be after longer-bodied underground arthropod larvae, the ones with shorter bills, the shorter ones." says Norton. "The birds might seem to be competing with each other. They’re not. They’re finely adapted."

With the annual melt, ponds and lakes appear throughout the region as well, and as water drains from the Brooks Range to the sea, rivers and streams tumble through the landscape. Occasionally, moisture accumulates under the tundra and freezes so that it pushes up the skin and creates ice-filled, vegetation-covered mounds, called pingos, measuring anywhere from 10 to 100 feet high.

Winged predators seek any vantage point they can to search for prey—foothills, the tops of pingos and the raised corners or centers of polygons. When McIntyre tracked her golden eagles to the North Slope, she could tell that they spread out across the entire region, but she couldn’t detect how they were using the habitat, which they shared with local golden eagles and other raptors. The newcomers surely dined well. "The slope during the summer is the land of lemmings, ground squirrels and lots of birds," points out Rothe.

Even the more subtle raised areas serve as upland habitat, providing dry patches for nesting and breeding. American golden plovers, for example, lay their light-colored eggs on dry Arctic ground in Alaska and Canada, in nests lined with light-colored lichens. Buff-breasted sandpipers use dry ground for their mating rituals. In what’s known as a lek mating system, males gather in these spots to compete for female attention by waving their wings in displays that even humans can see a mile away. The buff-breasted sandpiper is the only Alaska shorebird species known to mate in leks.

Biologist Richard Lanctot of the U.S. Fish and Wildlife Service in Anchorage studied the buff-breasted sandpiper’s mating behavior a decade ago. "We drove around a lot in a pickup on the oil fields, looking for wing waving," he says. Sometimes he also spotted the males doing territorial displays. "Two males fly up vertically, right next to each other, maybe 15 or 20 feet in the air," he describes. "They fly up almost like hummingbirds, call it off and fly back down again." After the females choose the winning males and mate, often at more than one site and with more than one male, they lay their eggs in moist or dry, meadowy tundra. About 40 percent of the world’s 15,000 buff-breasted sandpipers nest in Alaska. Affected by habitat loss along its migration path, the species also was overhunted in the late 1800s—"when they were shot by the wagonloads," says Lanctot.

WETLAND WONDERS: King eider females (left) troop along an island next to a coastal lagoon on the Arctic coast. These ducks feed on aquatic invertebrates and often nest on islands.

One concern about the buff-breasted sandpiper and other birds that use the coastal plain’s drier habitat is that developers also aim for higher ground—as evidenced by the oilfields at Prudhoe Bay. "There is no equivalent to wetland protection for upland sites," says Lanctot. "Frequently, roads get put into upland areas, and that’s where these birds like to hang out."

Birds that rely on wetter habitat have plenty of options. King eiders, for example, nest mostly on small islets in freshwater tundra ponds. Pacific and red-throated loons and their nests are never far from water, "because, of course, they can’t walk worth a darn," says Martin. Arctic terns, which fly here from the Antarctic ice pack in the longest migration of any bird, flutter above waterways and ponds to find and swoop down to catch small fish and invertebrates. Red-necked phalaropes nest in wet, thick sedges at the edges of polygon troughs or small ponds. With just a few steps they can be in water doing their spinning feeding dance, in which the birds pedal harder with one foot than the other to bring food to the surface, all the while pecking at the food 180 times a minute.

Some Arctic birds also travel far out to sea. "The whole field of satellite telemetry has opened a door to an understanding of bird movements that we haven’t had before," says Martin. One of the most striking examples was discovered in 1995, when a transmitter on a spectacled eider told scientists that the sea duck was in the middle of the Bering Sea in the dead of winter. Biologists who set out in a plane to find the bird were amazed to discover nearly the entire global population of the threatened species—about 400,000 birds—in one 40-mile-wide area of broken sea ice.

More recently, scientists using satellite transmitters have tracked snowy owls flying hundreds of miles across sea ice to locations in Siberia and Canada. "Everybody’s pretty excited to find out they’re oceanic owls," says Norton.

In and near the oilfields that have spread out from Prudhoe Bay over the past 30 years, ravens and gulls have taken advantage of a new kind of habitat: human garbage. Along with bears and foxes, these predator and scavenger species have exploited such areas and in many cases have thrived, also preying on other birds and their eggs. A recent National Academy of Sciences report on environmental effects of oil and gas activities on Alaska’s North Slope found that, as a result, some birds near these areas may have had a hard time maintaining their local populations.

LAKE FEEDER: A Pacific loon nests near a lake on the Arctic coastal plain that slopes north to the sea from the Brooks Range, which looms behind. The loon is never far from water, as it is an ungainly walker.

The oilfields are not the only places scientists are interested in relationships among species. Take, for example, the case of snowy owls, Steller’s eiders and lemmings in Barrow, the North Slope’s largest town. Home to about 4,500 people, Barrow also hosts concentrations of nesting snowy owls as well as most of Alaska’s breeding population of nesting Steller’s eiders, a threatened species. Why do these birds inhabit Barrow, especially when there appears to be plenty of similar habitat in other locations on the coastal plain?

"The best speculative answer I can give you has to do with lemmings," says Martin. In short, both owls and eiders tend to nest in years when lemming populations are high and not in years when they are low. "It’s been a puzzle for years why this association exists," he says. The owls of course depend in large part on the lemmings, but the eiders feed on aquatic insects and plants in ponds and streams. One theory is that predators gorging on lemmings tend to leave the eiders alone, and that somehow the eiders are programmed to take advantage of the cycle.

That still doesn’t explain why the birds are in Barrow. "It all leads back to the point that lemming population cycles seem to be more pronounced in Barrow then in other portions of the coastal plain," Martin explains. "So the birds’ presence may have nothing to do with the structural component of the habitat and everything to do with populations of lemmings."

Birds, after all, don’t exist alone here. Their droppings fuel the growth of plants, which in turn are eaten by animals large and small, from caribou to muskoxen to lemmings. And that may mean that what researchers are learning about birds in Alaska’s Arctic today will ultimately reveal a great deal more about the entire ecosystem.

Field editor Lisa W. Drew lives in Fairbanks, Alaska, where she watches for birds on their way to and from the Arctic.

NWF Takes Action Keeping the Arctic Refuge Wild

Dozens of species of birds and other wildlife could be affected by oil development on the coastal plain of the Arctic National Wildlife Refuge. For more than two decades, NWF has been providing information to U.S. lawmakers and the American public about the importance of this region to millions of animals. NWF’s most recent report, Arctic National Wildlife Refuge: Wildlife Values, provides additional evidence of this importance. "The refuge will be vulnerable to short-sighted development until Congress acts to permanently protect this spectacular place as wilderness," says Tony Turrini, director of NWF’s Alaska Project Office. To read the report, see our arctic refuge page.

ART BY ROBERT KEMP; SOURCE: U.S. FISH AND WILDLIFE SERVICE

How Birds Link the Arctic Refuge to Your Home

Every spring and summer, millions of birds migrate from the continental United States and other parts of the world to critical feeding, nesting and resting grounds in the Arctic National Wildlife Refuge. Some come from as far away as Antarctica. Among the attractions: the refuge’s diverse, pristine habitats and abundant seasonal food supplies.

Taking advantage of nearly round-the-clock daylight, the birds engage in intense nesting and chick-rearing activities. Researchers have recorded about 180 species of birds in the Arctic Refuge. Three-fourths of those species have been sighted on the reserve’s coastal plain, which includes the controversial 1.5 million acre parcel where proposed oil drilling would take place. That same parcel also provides crucial summer calving grounds for another large group of migrants: the 120,000 or so members of the Porcupine caribou herd.

Based on information and graphics supplied by the U.S. Fish and Wildlife Service, this illustration is not intended to show the exact migration routes several species follow when they fly south in late summer and fall to the lower 48 states. Nor does it point to their only destinations. But it does indicate some birds that may visit your area every year after leaving the Alaskan refuge.